Data processing systems frequency include a variety of types of memories, some of which may have different timing specifications. If the data processing system is used in a real-time application system, it may be useful during development to temporarily overlay small blocks of readily programmed memory, such as SRAM (Static Random Access Memory) over a portion of more difficult to program memory such as flash EEPROM (electrically erasable programmable read only memory) or ROM (read only memory) in order to allow the values obtained form the memory to be temporarily changed more readily. Additionally, in control systems a calibration process is commonly implemented prior to final production in which there is a remapping of pages of memory that contain different control parameters for purposes of fine tuning final production control parameters. For example, to fine tune or calibrate the behavior of an application, a set of program constant that application code is accessing may have to be modified by a user using an external tool connected to the processing system. The set of program constants must be made available coherently to the application code, and usually at some specific location in the execution of the code.
For development purposes address translation information is therefore required to be altered for one or more pages of memory by an external agent, such as a software or hardware development tool. Because a memory management unit (MMU) in a processing system can only be manipulated by an associated processor, the altering of address translation information may require the halting of the processor's execution to permit address translation alteration by a debug or scan port. Alternatively, the processor may be interrupted to permit software to remap the addressing. The remapping of memory is typically an intrusive operation that negatively effects system operation.
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